Dry friction clutch/brakes depend upon the rubbing of a dry friction material against dry reaction members to operate a press by selectively connecting a drive shaft of the press to a continuously rotating flywheel to start the press and selectively connecting the drive shaft to a non-rotatable or fixed member to stop the press. This rubbing action causes wearing of both the friction material and the reaction members as well as heat generation within these members. The faster the press operates and the faster the flywheel rotates, the greater the amount of wear and heat which is generated. This generation of heat and the associated wear requires periodic gap adjustment to keep the press operating correctly. In addition, there was no consideration given in the prior art dry friction clutch/brake units to an integral braking system for the flywheel itself. The braking system for the flywheel was normally done by a separate system external to the clutch/brake press drive.
The problems associated with the dry friction clutch/brakes led to the development of the oil shear brake and clutch drives. The oil shear brake and clutch drives use a hydraulic shearing action between two adjacent plates rather than the friction between the plates to transmit power. The oil shear system offers the advantages of little or no wear of the clutch or brake plates and virtually no brake fade. This provides a more precise operation of the press and dramatically increases press up-time. The oil film between the plates absorbs the heat generated by start-stops of the press. This removal of heat offers the advantages that there is now no practical limit in the press trip rate or the flywheel speed.
The oil shear clutch and brake systems have solved numerous problems associated with press drives, but there has been no consideration given to the braking of the flywheel. The prior art clutch/brakes were designed to connect and release the flywheel to the drive shaft or the press. Braking of the flywheel itself was accomplished by a separate brake unit, exterior to the oil shear clutch/brake unit and normally designed as a dry friction brake. The dry friction brake for the flywheel has all of the disadvantages of dry friction brakes mentioned above but also includes the problems associated with brake dust. When braking the flywheel, brake dust is released into the air. Since the presses are operating within a closed building, this contamination and polluting of the interior air is another problem which must be addressed.
Accordingly, there is a need for a clutch/brake assembly which utilizes oil shear technology for connecting the driveshaft of the press to the flywheel, but also incorporates a braking system operating with the oil shear system for braking of the flywheel.